Effects of Volume and Site of Blood Draw on Blood Culture Results

Abstract

Blood culture contamination greatly affects clinical decisions. Hence, it is of interest to assess the influence of factors such as the volume of blood drawn and the site of blood draw on the rates of blood culture contamination. In a retrospective study, blood cultures from infants and children up to 18 years of age who had at least one positive blood culture during the year 2006 were analyzed for their volume of blood drawn, patient's weight, site of blood draw used, and blood culture results. Blood cultures were deemed adequate collections if they contained an appropriate weight-related volume of blood. Moreover, blood culture results were categorized as true pathogens, contaminants, and negative cultures; these were then compared and analyzed with respect to their volume and site of blood draw. A total of 5,023 blood cultures were collected during 2006, of which 843 were analyzed. There were 306 (36%) positive cultures among the 843 cultures analyzed. Of the 306 positive cultures, 98 (32%) were contaminants and 208 (68%) cultures grew significant pathogens. Thirty-five percent of the contaminant cultures had adequate volume compared to 60% in the true bacteremia group (P < 0.001). Also, of the 843 cultures, the rates of contamination among the different sites of blood draw were as follows: peripheral venipuncture, 36%; arterial, 10%; and central venous access, 7% (P ‫؍‬ 0.155). The rate of contamination was higher with lower blood volumes, and there was no significant difference in the rates of contamination among the different sites of blood draw.Blood cultures are vital for identifying pathogens causing serious infections and in directing appropriate antibiotic therapy. Moreover, they remain the standard method for detecting bacteremia in the evaluation of sick patients (14). Unfortunately, blood culture contamination is a common occurrence and may lead to confusion regarding the significance of a positive blood culture. The most common contaminants are coagulase-negative staphylococcus species which are also becoming more prevalent as a primary pathogen in immunocompromised patients and in patients with indwelling intravascular devices (9, 15). The uncertain clinical significance of potential contaminants leads to longer hospital stays, unnecessary antibiotic therapy, and additional laboratory testing; as a result, the cost incurred by a hospital is many times that incurred by the laboratory (2).Many factors influence the yield of blood cultures, but the single most important factor is blood volume. Several studies have shown that the rate of isolation of pathogens from blood cultures increases with the quantity of blood submitted (12). Hence, a blood culture may be falsely negative from an inadequate-volume blood culture (6). Furthermore, the blood culture contamination rate inversely correlates with the volume of blood (3). The site and method of blood collection have also been known to influence the rate of contamination of blood cultures (8). Vascular-access devices, such as arterial and central venou...

Correlation between inoculum volume, positivity rates and microorganisms isolated from blood cultures

“…In this study, the overall incidence of positive results of 9.2% was lower than the internationally reported rate of 21.5-24.5% (Gonsalves et al, 2009;Bouza et al, 2007). A probable explanation could be due to the increased risk of mortality in patients with bacteraemia, in which there is generally a lower threshold for drawing blood culture samples, which increased our denominator (Bates and Goldman, 1991).…”

“…In addition, it also depends on the site where the blood is drawn from and on the volume of blood inoculated in the culture bottles (Connell et al, 2007;Gonsalves et al, 2009;Shafazand and Weinacker, 2002). Correct interpretation of the culture results is vital to initiate appropriate antimicrobial therapy in a patient, as contamination from skin flora is a common occurrence leading to misinterpretation of the results in certain clinical situations (Shafazand and Weinacker, 2002).…”

Antimicrobial susceptibility pattern in children with typhoid fever and serotype of Salmonella typhi in Jakarta

“…However the optimal volume of blood withdrawn would also affect the ability to detect infection in the blood. It is suggested that in infants and children the blood volume collected should be 0.5 ml for bodyweight less than 4 kilograms, while up to 5 ml for body weight of 4 kilograms [21]. Meanwhile WHO suggested volume of 5 ml for blood culture containing 45 ml broth, although it did not distinctively specify the age [2].…”

Taxa de contaminação de testes hematológicos e seus fatores determinantes

“…(7) The suppression of false positives to the highest possible extent is a measure of great impact, since this could prevent the realization of additional testing, the administration of possibly unnecessary medication, and increase the hospital stay of patients, implying an important finance expense. (5,(8)(9)(10) The main cause of contamination is linked to manipulation by the nursing staff, especially in hospital services with a large workload and limited time to work with each patient. (11) Following are highlighted some of the most relevant factors related to the practice itself, according to the literature.…”

“…A blood culture is considered to be contaminated if the presence of the following microorganisms is observed in 50% of all blood culture kits extracted in a day from a patient: S. coagulase-negative, alpha-hemolytic Streptococcus, Micrococcus species, Propionibacterium species, Corynebacterium species and Bacillus species. (4)(5)(6) According to the American Society for Microbiology the contamination levels of samples should not exceed 3%, although they frequently exceed 7%. (7) The suppression of false positives to the highest possible extent is a measure of great impact, since this could prevent the realization of additional testing, the administration of possibly unnecessary medication, and increase the hospital stay of patients, implying an important finance expense.…”